论文标题
Romulus25中孤立的超湿星系的形成
The Formation of Isolated Ultra-Diffuse Galaxies in Romulus25
论文作者
论文摘要
我们使用\ textsc {romulus25}宇宙学量量来识别{\ it Field} Ultra-diffuse Galaxies（UDGS）的有史以来最大的模拟样本。在$ z = 0 $时，我们发现孤立的UDGs具有平均的恒星形成率，颜色和病毒质量，适合其出色的质量和环境。 UDG的HI质量中等升高，比典型的孤立矮星型高70 \％（300 \％）比Luminosities的典型隔离矮星系高（fainter）比M $ _ \ Mathrm {B} $ = - 14。但是，UDGS与一般孤立的矮人星系人群一致，并弥补了$ \ sim $ 20 \％的所有现场星系中的百分比，其中10 $^7 $ <m $ <m $ _ \ star $/m $ $ _ \ odot $ <10 $^{9} $。 HI群众，有效的半径和UDG的总体外观与现有的UDG现有观察结果一致，但我们预测，当前的调查遗漏了许多孤立的UDG。尽管它们在$ z = 0 $时隔离，但我们样本中的UDG是主要合并的产品。在UDG中，合并并不比非UDG祖细胞更常见，但是创建UDG的合并往往会较早发生 - 几乎在$ z = 1 $之后永远不会发生，从而暂时增强旋转，并导致星形形成重新分发到银河郊外，从而导致较低的中心星星形成率。星系中心的中心随着中央恒星群体的年龄的年龄而逐渐消失，但是它们的全球恒星形成率是通过较大半径的恒星形成爆发来维持的，从而产生了更陡峭的负G-R颜色梯度。相对于孤立星系中UDG形成的其他建议，该地层通道是独一无二的，表明可以通过多种机制形成UDG。
We use the \textsc{Romulus25} cosmological simulation volume to identify the largest-ever simulated sample of {\it field} ultra-diffuse galaxies (UDGs). At $z=0$, we find that isolated UDGs have average star formation rates, colors, and virial masses for their stellar masses and environment. UDGs have moderately elevated HI masses, being 70\% (300\%) more HI-rich than typical isolated dwarf galaxies at luminosities brighter (fainter) than M$_\mathrm{B}$=-14. However, UDGs are consistent with the general isolated dwarf galaxy population and make up $\sim$20\% of all field galaxies with 10$^7$<M$_\star$/M$_\odot$<10$^{9}$. The HI masses, effective radii, and overall appearances of our UDGs are consistent with existing observations of field UDGs, but we predict that many isolated UDGs have been missed by current surveys. Despite their isolation at $z=0$, the UDGs in our sample are the products of major mergers. Mergers are no more common in UDG than non-UDG progenitors, but mergers that create UDGs tend to happen earlier - almost never occurring after $z=1$, produce a temporary boost in spin, and cause star formation to be redistributed to the outskirts of galaxies, resulting in lower central star formation rates. The centers of the galaxies fade as their central stellar populations age, but their global star formation rates are maintained through bursts of star formation at larger radii, producing steeper negative g-r color gradients. This formation channel is unique relative to other proposals for UDG formation in isolated galaxies, demonstrating that UDGs can potentially be formed through multiple mechanisms.
